Many many years ago, my very first girlfriend was sucking me off, when all of a sudden she went aaaaall the way down, balls-deep. However, she immediately went back to regular blowing, so I don't know whether that counts.
If that one doesn't count, then it was the first time I got blown by my current wife. It was a very passionate blowjob, and it soon turned to a throatfuck with me in control pumping all the way in and all the way out and all the way in and all the way out... I finished with my cock all down her throat and she swallowed everything.
